Machine for grinding gears



Aug. 2, 1966 M. ERHARDT MACHINE FOR GRINDING GEARS 5 Sheets-Sheet 1 Filed March 5, 1963 his ATTORNEY Aug. 2, 1966 M. ERHARDT momma FOR GRINDING GEARS 5 Sheets-Sheet 2 Filed March 5, 1963 L K m w N 5 ww m 6 A w Y B his A'ITDRNEY Aug. 2, 1966 M. ERHARDT 3,263,372

MACHINE FOR GRINDING GEARS Filed March 5, 1963 5 Sheets-Sheet 5 Ago! I INVENTUR. fred Erhardt BY 77110 2361 8- Sink r his ATTORNEY.

g- 1966 M. ERHARDT 3,263,372

MACHINE FOR GRINDING GEARS Filed March 5, 1963 5 Sheets-Sheet 5 INVENTOR.

Manfred Erha rdt BY Zfliefiozewzk his ATTORNEY United States Patent 3,263,372 MACHINE FOR GRINDING GEARS Manfred Erhardt, Munich, Germany, assignor to Carl Hurth-Maschinenund Zahnradfabrik, Munich, Germany Filed Mar. 5, 1963, Ser. No. 262,908 Claims priority, application Germany, Mar. 9, 1962,

16 Claims. in. 51-123 The present invention relates to grinding machines in general, and more particularly to a machine for grinding the teeth of work gears, such as shaving cutters, spur gears and other types of toothed workpieces. Still more particularly, the invention relates to an apparatus for generation grinding of gear teeth wherein a desired involute curve is ground on consecutive teeth of a work gear while the flanks of such teeth roll back and forth along the active surface or surfaces of one or more grinding wheels.

In conventional generation gear-tooth grinders of which I have knowledge at this time, a given tooth flank is treated by the active surface of a grinding wheel only when the work gear performs a forward rolling stroke or when the work gear performs a return rolling stroke. In other words, fifty percent of the time spent for grinding of tooth flanks on a given work gear is actually wasted with attendant loss in output, rapid wear on moving parts, cost involved in purchasing of additional machines to insure that a given number of work gears may be finished per unit of time, wasted manhours, and higher cost of the ultimate product.

Accordingly, it is an important object of my invention to provide an improved apparatus for grinding the teeth of work gears in a mass-manufacturing or in a smallerscale operation which can reduce the total time required for grinding the teeth of a given work gear by as much as fifty percent.

Another object of the invention is to provide an apparatus of the just outlined characteristics wherein a given tooth flank may be ground Within shorter periods of time and with greater precision than if such tooth flank were treated in heretofore known apparatus.

A further object of the invention is to provide an apparatus for grinding the teeth of work gears wherein some or all undesirable stresses which might tend to affect the speed and accuracy of the grinding operation are eliminated or compensated for in a very simple and eflicient manner.

Still another object of the instant invention is to provide a gear grinding machine which presents certain important advantages if the work gear is rolled by means of a pitch disk and steel tapes, and which is capable of reducing by as much as fifty percent the time necessary for grinding a Work gear even though it differentiates from known machines in respects which are rather minor when compared with the number of parts or assemblies of parts which can remain unchanged.

A concomitant object of the invention is to provide a generation grindingmachine for the teeth of work gears wherein the work gear is rolled by means of a pitch disk and one or more sets of flexible tapes and wherein any, even slightest, stretching or other deformation of tapes which could affect the accuracy of the grinding operation or the duration of the grinding operation is either compensated for or eliminated in a very simple and eflicient manner.

Another object of the invention is to provide a genera tion grinding machine wherein the grinding wheel or wheels are mounted in such a way that they may automatically compensate for some or all inaccuracies and/or irregularities in the rolling movement of work gears.

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A further object of the invention is to provide a gear grinding machine wherein the effect of some or all inaccuracies or irregularities in the rolling movement of the work gear with respect to one or more grinding wheels is compensated for or reduced by complementary movements of the wheel or wheels with respect to the work gear, by complementary movements of the Work gear with respect to the grinding wheels, or by simultaneous movements of the work gear and of the grinding wheels.

Still another object of the invention is to provide a novel wheel stand for use in a generation grinding machine of the above outlined characteristics.

An additional object of the invention is to provide a novel arrangement for rolling a work gear with respect to one or more grinding wheels in a generation grinding machine.

A further object of the invention is to provide a novel arrangement which prevents or which compensates for stretching of steel tapes used in generation grinding machines to bring about oscillatory movements of a pitch disk which causes the work gear to roll along the active surface or surfaces of one or more grinding wheels.

Another object of my invention is to provide a generation grinding machine wherein the active surface of a grinding wheel remains in requisite engagement with a given tooth flank of the work gear irrespective of the direction in which the work gear rolls with respect to the active surface.

One feature of my invention resides in the recognition that the grinding operation upon a tooth flank of the work gear can be completed within much shorter periods of time if the work gear is compelled to remain in uninterrupted operative engagement with the active surface of a grinding wheel, namely, not only during a forward rolling stroke but also when the work gear rolls back to its initial position to repeat the forward rolling stroke. By solving the problem of maintaining the active surface in uninterrupted operative engagement with the rolling tooth flank of a work gear or of maintaining the rolling tooth flank in uninterrupted operative engagement with the active surface of the grinding wheel, i.e., from the start to the very end of a grinding operation upon a given tooth flank, I achieve substantial savings in time necessary for grinding of a given tooth flank, for grinding of a given tooth, and for grinding of a given work gear so that the output of a generation grinding machine which embodies my invention is actually doubled with minimal or without any additional expenses.

If the grinding machine utilizes a pitch disk and one or more pairs of steel tapes which together serve as a means for reciprocating the work gear in a predetermined path and for simultaneously rocking the gear teeth about the axis of the work gear so as to roll a given tooth flank back and forth along the active surface of a revolving grinding wheel, at least some or any stretching of the tapes (such as invariably occurs in all known types of grinding machines) may be compensated for by intermittent stretching of the momentarily unstretched tape or tapes, by deformation of the tapes which are being stretched to compensate for the extent of stretch and to thereby prevent undesirable stray movements of the tooth flank with respect to the active surface of the grinding wheel, and/or by preventing any or by preventing at least some stretching of tapes by subjecting the pitch disk to the action of compensatory forces which prevent it from moving beyond two predetermined end positions.

According to another feature of my invention, stretching of tapes may be compensated for by initial adjustment in the position of the work gear and/ or of the grinding wheel in such a way that only one set of tapes is subjected to intermittent stresses which compensate for stretching whereas the other set of tapes is permitted to become deformed and to thereby actually permit the work gear to remain in operative engagement with the active surface of a grinding wheel.

According to a further feature of my invention, the tapes are permitted to stretch and allow the work gear to roll back and forth in a path which is not the ideal path whereas the grinding wheel, in addition to rotating about its axis, is caused to per-form compensatory movements substantially in the axial direction thereof to compensate for stray movements of the rolling tooth flank such as are caused by stretching of the tapes.

Of course, it is equally within the scope of my invention to compensate for stray rolling movements of a given tooth flank in response to undesirable stretching of the tapes by compensating for some stretching and by providing for compensatory movements of the grinding wheel so that such compensatory movements and such compensatory stretching together contribute to retain the tooth flank in uninterrupted operative engagement with the active surface of a grinding wheel.

Finally, it is also possible not to compensate for stray movements of the work gear but to prevent such stray movements, for example, by generation of forces which positively prevent any angular displacements of the pitch disk or of other rolling motion producing means beyond two predetermined end positions in and between each of which the pitch disk holds the tooth flank in engagement with the active surface of the work gear.

In view of the multiplicity of in part different steps which may be resorted to in the practice of my invention, the apparatus can assume a number of forms. Thus, it is possible to modify an existing generation gear grinding machine by incorporating therein means which compensates for undesirable stretching of the tapes, either by subjecting such tapes to tensioning or by subjecting such tapes to bending or deflecting stresses. Furthermore, it is possible to provide means other than or supplementing the action of tapes to cause angular movements of the pitch disk and to limit such angular movements to the extent necessary for insuring that the flank of a tooth on the Work gear remains in continuous operative engagement with the active surface until the grinding operation is completed in response to repeated rolling of the tooth flank back and forth along the active surface. Furthermore, and if the machine does not comprise any means to compensate for or to eliminate undesirable stretching of the tapes, the work stand may embody novel compensating means which compels the active surface of the grinding wheel to follow some or all stray movements of the tooth flan-k at the time the flank rolls back and forth in response to combined oscillatory and linear movements of the pitch disk or of other rolling motion producing means, and such compensating means is preferably connected with the carriage for the pitch disk to compel the grinding wheel to reciprocate axially in rhythm with rolling movements of the work gear.

-In one of its preferred forms, the machine of my invention may carry out the steps of reciprocating the work gear in a predetermined path and simultaneously rocking the gear teeth about the axis of the gear so that a given tooth flank is compelled to perform back and forth rolling movements with respect to and along the active surface of a revolving grinding wheel whereby the work gear is automatically subjected to the action of disengaging forces (such as inertia of the means which moves the work gear, friction, shifting in the position of the centers of gravity of parts which move with the work gear, etc.) which tend to bring about stray movements of the flank in a direction to separate the flank from the active surface during one of alternating movements of the flank (i.e., when the flank rolls back or forth with respect to the active surface), and subjecting the work gear and/ or the grinding wheel to stresses which oppose and/or which compensate for such disengaging forces so that the flank remains in uninterrupted engagement with the active surface.

For example, it is possible to subject only the work gear to stresses which retain the flank in engagement with the active surface irrespective of the direction in which the flank is caused to roll. On the other hand, the work gear may be permitted to yield to disengaging forces so that it moves from the ideal path while rolling back or forth with respect to the active surface; in such instances, the grinding wheel is moved toward the flank whenever the latter leaves the ideal path so that the active surface actually follows the flank and remains in uninterrupted engagement therewith. Furthermore, it is possible to subject the work gear to stresses which oppose and which partially compensate for such disengaging forces to reduce the extent of stray movements of the flank, and to move the grinding wheel in response to such rolling movement of the flank during which the flank tends to become separated from the active surface so as to compensate for the remainder of disengaging forces and to insure that the active surface is retained in uninterrupted engagement with the flank.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The grinding machine itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a schematic front elevational view of a grinding machine which embodies one form of my invention;

FIG. 2 is a schematic side elevational view of the machine as viewed from the left-hand side of FIG. 1;

FIG. 3 is a greatly enlarged fragmentary vertical section as seen in the direction of arrows from the line IIIIII of FIGS. 2 and 6;

FIG. 4 is a vertical section as seen in the direction of arrows from the line IV-IV of FIG. 3;

FIG. 4a illustrates a different position of a three-way valve which is shown inFIG. .4;

FIG. 4b illustrates a further position of the three-way valve;

FIG. 40 shows a motion transmitting connection for a slide valve which is illustrated in FIG. 4;

FIG. 5 is an enlarged perspective view of a slightly different pitch disk and of the actual grinding station;

FIG. 6 is an enlarged fragmentary vertical section as seen in the direction of arrows from the line VIVI of FIG. 3;

FIG. 7 is a fragmentary section as seen in the direction of arrows from the line VII-VII in FIG. 6;

FIG. 8 is a section similar to the one illustrated in FIG. 3, but showing a third system which compensates for unequal dcformation of steel tapes, this system comprising a pair of one-way clutches;

FIG. 9 is a transverse vertical section through one of the clutches as seen in the direction of arrows from the line IX-IX of FIG. 8;

FIG. 10 is a transverse vertical section through the other clutch as seen in the direction of arrows from the line X X of FIG. 8;

FIG. 11 is a fragmentary perspective view of a different grinding machine wherein the tapes are tensioned by direct engagement with levers or similar deforming means;

FIG. 12 is a section as seen in the direction of arrows from the line XIIXII of FIG. 11;

-FIG. 13 is an axial section through the spindle of the grinding wheel, further showing an additional system which may compensate for undesirable displacements of the work gear with respect to the grinding wheel; and

FIG. 14 is a section as seen in the direction of arrows from the line XIVX1V of FIG. 13.

Referring now in greater detail to the drawings, and first to FIGS. 1 to 6, there is shown a machine which is utilized for grinding the flank 100 on a work gear 25, see FIG. 5. The flanks 100 are treated while rolling back and forth along the annular active surface 107 of a rotary grinding wheel 75. Such type of gear grinding is called generation grinding. In this embodiment of my invention, the means for rolling the tooth flanks 100 along the active surface 107 of the grinding wheel 75 comprises a rockahle segment-shaped element 28, called pitch disk, and one or more pairs of specially mounted flexible tapes 29 which are usually made of steel.

As shown in FIG. I, the grinding machine comprises a main frame F including a base or bed whose upper side is provided with horizontal ways 20a (see FIG. 3) for the rails 22 of a gear supporting means here shown as :a reciprocable carriage 21. The carriage 21 is reciprocable in a linear path which is perpendicular to the planes of FIGS. 1 and 3. The device for reciprocating the carriage .21 with respect to the base 20 is well known in the art and, therefore, is not shown in full detail.

The carriage 21 supports bearings for a hollow hori zontal shaft 23 (hereinafter called sleeve) which serves as a support for the pitch disk 28 and whose axis is perpendicular to the longitudinal extensions of the ways 20a. The sleeve 23 is rotatable in but is held against axial movements with respect to the carriage 21, and this sleeve accommodates a gear-supporting work spindle 24 which is held against axial movements but is freely rotatable therein. One end of the work spindle 24 mounts the work gear 25 and its other end is operatively connected with an indexing head 26 of known design which serves as a means for normally coupling the spindle to the sleeve 23 and for intermittently changing the angular position of the work gear 25 whenever it becomes necessary to move another tooth flank 100 into engagement with the active surface 107 of the grinding wheel 75. Thus, when the machine is in actual use, the gear 25 is rigid with and shares all movements of the sleeve 23 and of the pitch disk 28. The mounting of the sleeve 23 and of the spindle 24 is preferably such that they may rotate in common antifriction bearings. For example, such antifriction bearings may assume the form of roller thrust bearings which are pressfitted into the carriage 21 in order to eliminate or to reduce the tolerances. The present invention is not concerned with the exact construction of antifriction bearings for the parts 23, 24; therefore, such bearings have been omitted in the drawings.

The means for adjustably and detachably securing the pitch disk 28 to the sleeve 23 comprises a series of bolts 27 (see FIG. 3), and the grinding machine of FIGS. l-6 comprises two pairs of steel tapes 29a, 29b and 29c, 29d whose longitudinal extensions are perpendicular to the axis of the sleeve 23. As best shown in FIG. 5, one end portion of each tape is secured to one of two radial faces of the segmental pitch disk 28, as at 28a, the other end portions of the tapes 29a, 29b are mounted at the first end portion 31 of a horizontal holder 31, and the other end portions of the tapes 29c, 29d are mounted at the second end portion 31" of the holder 31. Thus, the outer end portions of the tapes 29a-29d are operatively connected with the frame F because the holder 31 is mounted on the frame even though it can perform certain movements with respect thereto. The means for connecting the tapes at the respective end portions of the holder 31 comprises a series of bolts 30, shown in FIGS. 4 and 6. The holder 31 is perpendicular to the axis of the sleeve 23 and is provided with an upwardly extending dovetailed rail 31a which is slidable in a complementary groove 32:: of a supporting member here shown as a crosshead 32. Suitable means (to be describe-d in connection with FIG. 6) are provided to arrest the holder 31 in any of a number of positions with respect to the cured to a frame member or block 33 which is connected to the frame F (see FIGS, 1, 2 and 4) and which is provided with means for adjusting the position of the crosshead 32. The adjusting means comprises vertical guideways 34 forming part of the block 33 and engaging the crosshead 32 so that the latter is held. against all other but vertical movements, an externally threaded vertical spindle 35 which is secured to the block 33, and a spindle nut 36 which is fixed to the crosshead 32 and which mates with the spindle so that, when the spindle is rotated in a clockwise or anticlockwise direction, the crosshead 32 is compelled to move up or down along the guideways 34. The means for rotating the spindle may assume the form of a suitable wrench or the like which is applied to a polygonal head 37 at the upper end of the spindle. Lock screws 38 are provided to arrest the crosshead 32 in selected positions of adjustment with respect to the block 33.

The left-hand end portion 32b of the crosshead 32, as viewed in FIG. 2, is supported by a second block 39. The adjustable connection between the end portion 32b and the block 39 comprises a vertical slot 40 provided in the end portion 32b and one, two or more retaining bolts 41 which are screwed into the block 39.

The longitudinal ends 31', 31 of the holder 31 support crossbars 42a, 42b which act not unlike swingletrees and whose central portions are respectively secured to tensioning levers 44a, 44b by means of screw bolts 43a, 43b, see particularly FIGS. 3 and 6. The levers 44a, 44b are respectively mounted on horizontal pivot pins 45a, 45b and these pins are respectively mounted in bearing brackets 46a, 46b. The brackets 46a, 46b are fixed to the holder 31 by means of bolts 47a, 47b. Since the manner in which the levers 44a, 44b respectively ten sion the tapes 29a, 29b and 29c, 29d is the same, it is sufficient to described the device which operates the lever 44a, and this description will be made mainly with reference to FIG. 6. The lever 44a is formed with an upwardly extending open slot 48 which accommodates a pin 50, the latter being carried by a spindle nut 49 which mates with external threads of a spindle 51a rotatable in the bracket 46a. This spindle 51a is provided wih a noncircular end portion 52 which may be engaged by a wrench or the like in order to change the axial position of the spindle nut 49 and to thereby pivot the lever 44a about the pin 45a. The entire spindle 51a is axially movable in the bracket 46a and constitutes the piston rod of a piston 54a which is accommodated in a cylinder 55a, the latter forming an integral part of or being connected to the bracket 46a and defining a cylinder chamber 56a which is adjacent to the left-hand side of the piston 54a, as viewed in FIG. 6. The chamber 56a communicates with a fluid-admitting or evacuating port 57. In the chamber 56a, there is provided an internal stop shoulder 53a against which the piston 54a abuts when the pressure of fluid in the cylinder 55a drops. The piston 54a abuts against the shoulder 53:: when the tapes 29a, 29b tend to rock the lever 44a in an anticlockwise direction, as viewed in FIG. 6.

The other lever 44!) cooperates with a. second spindle 51b (see FIG. 6) which extends through a second cylinder 55b (FIG. 4) whose internal chamber 56b communicates with a conduit 57b, the latter corresponding to a conduit 57a which is connected to and communicates with the port 57 of the cylinder 55a.

The rail 31a of the holder 31 is slidable in the groove 32a of the crosshead 32, and this holder is permanently biased against the shorter arm 63 of a two-armed lever 61 by means of a helical spring 58 which is shown in FIG. 6. The eye 58a at one end of the spring 58 engages a suitably configurated projection or retainer 31b of the holder 31, and the other end 581: of this spring is convoluted around a nut 59 which mates with a screw bolt 60. The head of this bolt is received in a horizontal bore of the crosshead 32 and may be reached by the tip of a screwdriver to adjust the tension of the spring 58 and to thereby adjust the force with which a projection 310 of the holder 31 bears against the lower arm 63 of the lever 61. This lever is rockable about a horizontal pin 62 which is secured to the crosshead 32, and the upwardly extending longer arm 64 of the lever carries an arresting member 65 whose head normally abuts against the head of a stop 66 provided in and secured to a horizontal adjusting member 67 which is reciprocable in a suitable bore 32d of the crosshead 32 and which is held against angular displacements by a key 68. The member 67 is formed with internal threads 69 which mate with external threads of a motion-transmitting element 6911, the latter being provided with a worm wheel 70 which mates with a worm 71 so that, in response to rotation of the motion-transmitting element 69a, the stop 66 may be moved with the adjusting member 67 in order to rock the lever 61 against the bias of the spring 58 or to permit the lever 61 to be rocked by this spring in an anticlockwise direction, as viewed in FIG. 6. The means for rotating the worm 71 may comprise a suitable wrench or the like which rotates theworm shaft in the same way as described in connection with the spindle 51a.

A dial gauge 72 is provided with a spring-biased shaft 72a which abuts against the upper arm 64 of the lever 61 so that the gauge 72 may indicate the position of the holder 31. When the holder 31 is moved to a desired position wit-h respect to the crosshead 32, it may be fixed in such position by a hand-operated locking device 73 which is shown in FIGS. 2 and 4.

The heretofore described parts of the gear grinding machine enable an operator to move the work gear 25 in a number of different directions such as are necessary to insure that the tooth flanks 100 will roll along the active surface 107 and that the indexing head 26 may move consecutive flanks into engagement with the grinding wheel 75. In this embodiment, novelty resides in the provision of a compensating system shown in FIGS. 4 and 6 which regulates the tension of tapes 29a-29c so as to insure that the active surface 107 will grind a tooth flank 100 irrespective of the direction in which the pitch disk 28 rocks about the axis of the spindle 24.

Reference will now be made to FIG. 13 which shows the mounting of the grinding wheel 75. This wheel rotates in a headstock 76 which is movable vertically in and is tiltable with respect to a wheel stand 77. The headstock 76 may be fixed in any desired position of adjustment so that the active surface 107 of the grinding wheel 75 may assume a requisite position relative to the work gear irrespective of the diameter and of the configuration of tooth flanks on the work gear. Such mounting of the headstock 76 is well known and, therefore, has not been shown in the drawings.

The grinding wheel 75 is connected with one end of a tool spindle 78 which is mounted in special bearings including a conical bearing sleeve 79 and a cylindrical bearing sleeve 80. A helical expansion spring 81 serves to eliminate axial play of the spindle 78 by urging the conical portion 78a of the spindle into full contact with the internal surface of the bearing sleeve 79 and by engaging a thrust bearing 82 which is held in a selected position of adjustment by two lock nuts 83, the latter serving as a means for adjusting the bias of the spring 81. The lefthand end of the spindle 78 is connected with a flexible coupling 85 which is driven by an electric motor 84.

The bearing sleeves 79, 80 form integral parts of or are connected to a spindle sleeve 86 which is axially movable in but which cannot rotate with respect to the headstock 76. Axial movements of the sleeve 86 are necessary to compensate for dressing of the grinding wheel 75, and such movements are brought about by a spindle nut 87 which is rigid with the sleeve 86, which meshes with an adjusting spindle 88, and which is provided with known means (not shown) to prevent axial play of the spindle.

The spindle 88 is rotatable in the headstock 76 and carries a spur gear 89 which mates with a second spur gear 90 on an intermediate shaft 91. The shaft 91 is rotatable in the headstock 76 and carries a bevel gear 92 meshing with a bevel gear 93 which is mounted on the inner end portion of a shaft 94 whose outer end portion 95 of noncircular shape may be engaged by a suitable tool to angularly displace the shaft 91 and to thereby change the axial position of the sleeve 86 so as to compensate for dressing of the wheel 75. The grinding wheel 75 is preferably surrounded by a protective housing 7611 which has an opening large enough to permit engagement between the active surface 107 and a tooth flank 100.

The remaining parts of the structure shown in FIG. 13 and FIG. 14 will be described hereinafter subsequent to description of the operation which may be carried out by the apparatus of FIGS. 1-6 and subsequent to description of certain other embodiments of my invention.

Referring now to FIG. 5, the illustration therein shown is best suited for describing the manner of grinding the tooth flanks 100. As is customary in the art of grinding machines which utilize a pitch disk and steel tapes, the flank of the tooth 25a on the work gear 25 is treated by the revolving surface 107 of the wheel 75 while the carriage 21 moves back and forth along the ways 20a (see the arrows 101, 102). Since the pitch disk 28 is turnable about the axis of the sleeve 23 (not shown in FIG. 5) which is mounted in the carriage 21, and since the outer ends of the tapes 2961-29d are fixed to the crossbars 42a, 42b which are mounted on the holder 31 (which latter, in turn, is indirectly fixed to the machine frame F), the pitch disk 28 is compelled to rock or to oscillate in directions indicated by the arrows 103, 104 as soon as the carriage 21 begins to reciprocate along the ways 20a. Owing to such oscillatory movements of the pitch disk 28, the tooth flank 100 is compelled to roll along the active surface 107 (see the arrows 105, 106). It is assumed here that the grinding wheel 75 is held against axial movement (spring 81) and that it merely rotates about the axis of the sprindle 78 as soon as the motor 84 is started. At a first glance, a person not fully familiar with the art of such machines would assume that the tooth flank 100 will automatically roll along the active surface 107 not only when the work gear 25 turns in a clockwise direction (arrow 105) but also when the work gear turns in the opposite direction (arrow 106). However, in actual practice, and in the absence of any compensation for movements of the :tooth flank 100 other than in directions indicated by the arrows 105, 106, this flank will be treated in a desired way only when the gear 25 turns in the direction of the arrow 105 or 106, i.e., when the pitch disk 28 is rocked in a clockwise direction (arrow 103) or in the opposite direction (arrow 104). Thus, and assuming that this is a conventional grinding machine, the flank 100 will roll along the surface 107 when the carriage 21 moves to the right (arrow 102). Consequently, and if the grinding operation is carried out in a desired manner only when the gear 25 rotates in an anticlockwise direction (arrow 106) and when the carriage 21 moves to the right (arrow 102), the flank 100 moves away from the surface 107 when the gear 25 turns in the opposite direction (arrow 105). In other words, no shavings or chips will normally be removed from the flank 100' during each second stroke of the carriage 21 which means that onehalf of the total time necessary for grinding a tooth flank is wasted.

I have found that, in a machine which operates with a pitch disk and steel tapes, the :reason for movement of tooth flanks toward or away from the active surface of the grinding wheel is mainly due to undesirable stretching of tapes. Such stretching is caused by inertia, by gravity, by friction, and by other forces which arise as a result of reciprocatory movements of the carriage, of the work gear and of the pitch disk. Among others, undesirable deformation of tapes is due to changes in the angular position of the pitch disk 28 whose center of gravity shifts with respect to the axis of the spindle 24 when the pitch disk is caused to oscillate in response to reciprocation of the carriage 21. Thus, the tape 29c will be stretched more than the tape 29a when the carriage 21 moves to the right (arrow 102), and the extent of such difference in stretching of tapes 290, 29a is indicated (greatly exaggerated for the sake of clarity) at 110. In other words, the stretch of the tape 29c exceeds the stretch of the tape 29a by the distance 110 when the pitch disk 28 turns in an anticlockwise direction (arrow 104). As a result of such unequal stretch of tapes 29a, 290, the tooth flank 100 moves toward the active surface 107 and covers a distance 110' which approximates or equals the distance 110. In other words, the distance 110 represents the spacing of the flank 100 from the line 109 which is the ideal line of contact between the surface 107 and the tooth 25a. Consequently, the grinding wheel 75 should also move through a distance 110 in Order to insure that the contact pressure between the surface 107 and the flank 100 remains the same regardless of the direction in which the carriage 21 moves along the ways 20a.

On the other hand, at least when the carriage 21 begins begins to move in a direction to the left (arrow 10]), the stretch of the tape 2% exceeds the stretch of the tape 29c whereby the flank 100 moves away from the surface 107 and the tooth 25a is actually out of contact with the grinding wheel. Thus, the stretch of tapes 29a, 290 is undesirable regardless of in which direction the carriage 21 moves along the ways 20a because, on the one hand, stretching of the tape 290 permits the flank 100 to bear with excessive pressure against the surface 107 whereas, when the tape 2% is stretched, the flank 100 may move out of contact with the surface 107. It is to be noted that, for the sake of simplicity, FIG. 5 shows only two steel tapes and that the outer ends of these tapes are being shown as connected directly to the end portions 31, 31" of the holder 31 rather than to the crossbars 42a, 42b as illustrated in FIG. 6.

In accordance with my invention, the machine of FIGS. 1 to 6 comprises means capable of compensating for undesirable deformation of steel tapes and for resultant stray movements of teeth 25a, and such compensating means is arranged to compensate for deformation of tapes in a way to insure that the flank 100 remains in requisite contact with the active surface 107 not only during each forward stroke but also during each return stroke of the carriage 21 so that the time necessary for grinding the flank is cut in half. The compensating means normally does but need not always fully compensate for all deformations of the tapes as long as the machine is capable of grinding a tooth flank without interruptions, i.e., while the work gear is rocked about its axis in a clockwise or in an anticlockwise direction. One form of such compensating means has been described in conection with FIGS. 4 and 6. Thus, and as best shown in FIG. 5, the piston 54a in the cylinder chamber 56a may be moved by pressure of oil or another fluid which is admitted through the port 57 so that the piston moves away from the stop shoulder 53a and rocks the tensioning lever 44a in a clockwise direction to thereby increase the tension of tapes 29a, 2% by shifting the respective end portions of these tapes away from the pitch disk 28. The port 57 may receive pressure fluid through the aforementioned conduit 57a which leads to a three-way valve 113, see FIGS. 4, 4a and 4b. The valve 113 may receive or discharge fluid through a connecting line 112 leading to a slide valve 111 which is connected with a supply conduit 117 containing a pump P and leading to a source of pressure fluid here shown as an oil tank T. The valve 111 is further connected with a conduit 117a which returns spent fluid to the tank T. The conduit 5717 which is also connected to the three-way valve 113 leads to the aforementioned second cylinder chamber 56b so that fluid admitted into this cylinder chamber may cause the tensioning lever 44b to pivot in an anticlockwise direction, as viewed in FIG. 6, and to tension the tapes 29c, 29d in synchronism with the operation of the grinding machine by shifting the outer end portions of these tapes away from the pitch disk 28.

Such tensioning or shifting of the tapes 29a-29d in synchronism with the operation of the machine is brought about by a rotary cam 114 which cooperates with a roller follower 115 provided at one end of a valve member 116 forming part of the slide valve 111. The cam 114 is operatively connected with the carriage 21 (the operative connection is indicated schematically at 114a in FIG. 40) so that it is rocked back and forth in response to reciprocatory movements of the carriage (arrows 101, 102 in FIG. 5). The connection 114a may comprise a rack fixed to the carriage 21 and a pinion connected to the cam 114 and mating with the rack to insure that the valve member 116 will move back and forth in response to reciprocation of the carriage 21. Other types of operative connections may be used if desired. The valve member 116 is under the bias of a valve spring 116d which causes the follower 115 to track the lobe of the cam 114.

In the position of FIG. 4, the three-way valve 113 permits outflow of fluid from the conduits 57a, 57b into the connecting line 112, and the valve member 116 permits such fluid to flow through the return conduit 117a and back to the tank T. In other words, no compensation for undue stretching of the tapes 29a29d takes place. If the valve 113 is adjusted to assume the position of FIG. 4a, and if the cam 114 shifts the valve member 116 to a position in which the valve member permits flow of pressure fluid from the conduit 117 to the line 112, the conduit 57a admits pressure fluid into the cylinder chamber 56a and the tensioning lever 44a is pivoted in a clockwise direction, as viewed in FIG. 6, so as to stretch the tapes 29a, 29b (arrow 118) and to bias the tooth 25a in a direction to the left, as viewed in FIG. 5, whereby the flank is prevented from moving through the distance and remains in requisite contact with the active surface 107. In other words, the grinding wheel 75 may remain in the axial position of FIG. 5.

If the valve 113 assumes the position of FIG. 4b, the conduit 57a is sealed from the pump P but the conduit 57b receives pressure fluid to insure that the lever 44b pivots in an anticlockwise direction, as viewed in FIG. 6, and prevents the flank 100 from moving away from the surface 107. Thus, merely by changing the position of the valve 113 (between the positions of FIGS. 4a and 4b) and by providing an operative connection 114a between the valve 111 and the carriage 21, I insure that any stretching of tapes is compensated for in a sense to retain the tooth 25a in a desired position with respect to the surface 107 not only when the carriage 21 moves in one direction but also when the carriage moves in the opposite direction. The valve 113 is operatively connected with the carriage 21 (see the phantom-line connection 113a in FIG. 4a) to insure that it alternately permits flow of pressure fluid to the chambers 56a, 56b in synchronism with the operation of the machine. Of course, the tooth 25a is still free to roll along the surface 107 (arrows 105, 106) in order to insure that the flank 100 is treated from the root and toward the outer end of the tooth or vice versa, depending on the direction of such rolling movement. The purpose of the crossbars 42a, 42b is to respectively subject the tapes 29a, 29b and 29c, 29:1 to equal tension.

In many instances, it is sutficient to compensate for stretching of one set of tapes (29a, 29b or 29c, 29d). Thus, and assuming that the valve 113 remains in the po- -inner clutch elements through the balls 130, 131.

sition of FIG. 4a and that the valve 111 is operated by the carriage 21 to alternately admit fluid to the chamber 56a and to prevent escape of fluid from this chamber, the lever 44a will tend to stretch the tapes 29a, 29b to such an extent that the tooth 25a will attempt to move through a distance 119 (see FIG. while rolling in a direction as indicated by the arrow 105. The distance 119 is shown as equaling about twice the distance 110'. The gear 25 then cooperates with the wheel 75 to assume a position in which it remains in constant engagement with the surface 107 by compensating for the stretch of tapes 29c, 29d (distance 110).

Referring now to FIGS. 8 to 10, there is shown a different grinding machine wherein excessive stretching of tapes in response to reciprocation of the carriage 21 is prevented by additional angular displacement of the pitch disk 28 or by reducing the extent of such angular displacement. In this embodiment, the tapes are not stretched at all (beyond the initial stretch) because the angular displacements of the pitch disk are controlled by means other than the carriage 21'.

The sleeve 23 of the pitch disk 28 is rigid with a pair of inner clutch elements 126, 127 which form part of two one-way clutches. Thus, the elements 126, 127 are normally rigid with the spindle 24. The inner clutch elements 126, 127 respectively cooperate with outer clutch elements 128, 129 through interposed spring-biased balls 130, 131 which may be replaced by suitable sprags as is well known in the art of such clutches. The clutches comprise a series of balls 130, 131 which are accommodated in suitable cutouts provided in the peripheries of the respective inner clutch elements 126, 127. The halls 130 compel the inner clutch element 126 to transmit rotary motion to the sleeve 23' when the outer clutch ele ment 128 rotates in an anticlockwise direction (arrow 132 in FIG. 9). On the other hand, the inner clutch element 127 will transmit rotary motion when the outer clutch element 129 rotates in a clockwise direction (arrow 133 in FIG. Thus, the outer clutch element 129 is free to rotate in an anticlockwise direction, and the outer clutch element 128 is free to rotate in a clockwise direction, as viewed in FIGS. 9 and 10.

The peripheral portions of the outer clutch elements 128, 129 assume the form of pinions 134, 135 which respectively mesh with two racks 136, 137, each of these racks having at its opposite ends cores 138, 139 extending into solenoid coils 140, 141, respectively. The coils 140, 141 are mounted on the carriage 21. Each rack is biased by a spring 141a in such direction that the outer clutch elements 128, 129 tend to rotate in directions respectively indicated by the arrows 132, 133 and to entrain the Consequently, and when the coils 140, 141 are not energized, the racks 136, 137 are compelled to move back and forth in response to angular displacements of the pitch disk 28 whenever the carriage 21' is caused to reciprocate along the ways a. If the solenoid coils 140, 141 are energized in synchronism with reciprocatory movements of the carriage 21, they may hold the pitch disk 28 against further angular displacement and thereby prevent excessive stretching of the tapes. It is also possible to energize the coils 140, 141 in such sequence that they provide an additional force for turning the pitch disk 28 and that they thereby compensate for changes in the position of the center of gravity of the pitch disk, for friction and for other influences which tend to subject the tapes to undue stretch, Thus, uncontrolled stretching of the tapes is minimal or is eliminated entirely so that the flank 100 merely rolls along the active surface 107 without moving axially of the grinding wheel. In other words, the compensating means of FIGS. 8 to 10 prevents movements of the flank 100 through the distance 110 or 119 by preventing undue stretching of the tapes (distance 110 in FIG. 5).

The compensating means of FIGS. 8-10 may be called 12 a braking device which serves to prevent undesirable movements of the pitch disk 28 and to thus eliminate stray movementsyof the tapes.

Referring to FIGS. 11 and 12, there is shown a portion of a further grinding machine which again comprises a pitch disk 28 and two pairs of steel tapes 29a, 29b and 29c, 29d. The outer end portions of the tapes are secured to crossbars 42a, 42b which are carried by the holder 31, not shown in FIG. 11. The tensioning levers 44a, 44b and the associated hydraulic or pneumatic systerns of FIG. 6 are omitted because the stretch of tapes 29a-29d is controlled by tensioning or deflecting elements 142a, 142b which are moved into direct deflecting engagement with intermediate portions of the tapes or which are in permanent engagement therewith. The carriage 21 supports a cam shaft 241 which forms part of the deflecting means by supporting and by transmitting motion to the elements 1420!, 142b. The shaft 241 may be rocked in response to reciprocation of the carriage to move the deflecting elements 142a, 1421) toward or away from the .tapes 29a, 2%. A similar shaft and similar deflecting elements may be provided to stretch the tapes 29c, 29d.

One end of the shaft 241 carries a lever 143 which is swingable between a pair of adjustable stops 144, 145. For example, the stop 144 may assume the form of a screw which is rotatable with respect to a stationary part Fa of the machine frame, whereas the other stop 145 may resemble a rotary eccentric disk which may be adjusted by hand to change the extent of angular movements of the shaft 241. Of course, it will be readily understood that the stop 144 may be replaced by an eccentric disk similar to the disk 145 or vice versa.

The other end of the shaft 241 is connected with a link 146 which is articulately connected to a push rod 147 extending through a friction clutch 148 turnably fixed to a supporting member 149. The supporting member 149 is fixed to the machine frame, for example, to the crosshead 32. As shown in FIG. 12, the clutch 148 comprises a housing 150 which is provided with a through bore for the push rod 147. A second bore of the housing 150 which is perpendicular to the axis of the rod 147 accommodates a friction generating element or plug 153 which bears against the push rod under the bias of a spring 151, and this spring is held in its bore by a detachable cover 152. As the carriage 21 moves back and forth (see the arrows 101, 102), the push rod 147 is caused to move against the bias of the spring 151 but is arrested as soon as the carriage comes to a halt. The cam shaft 241 is rocked back and forth and moves the deflecting elements 1420, 142b against the tapes 29a, 29b (arrow 154) or away from the tapes (arrow 155) to insure that the flank 100 of the tooth 25a remains in contact with the active surface 107. The deflecting elements 142a, 1421) exert upon the respective tapes a bending stress which is active in a direction at right angles to the longitudinal extensions of the tapes and which causes additional rolling movements of the tooth 25a or prevents undesirable movements of the work gear. The extent to which the elements 142a, 142b deflect the respective tapes may be adjusted by the stops 144, 145.

An important advantage of the compensating means shown in FIGS. 11 and 12 is that comparatively small forces, acting in directions at right angles to the longitudinal extensions of the tapes (deflecting elements 142a, 142b) suflice to deform the tapes to the extent necessary to retain the flank of a gear tooth in requisite engagement with the active surface of a grinding wheel. All that is necessary is that the deflecting forces acting upon the tapes in response to rocking of the cam shaft 241 should have a component which is perpendicular to the longitudinal extensions of the tapes. Such deflection causes a reduction in the effective length of the tapes so that the tapes permit only such movements of the pitch disk and of the work gear which are necessary to retain a tooth flank in engagement with the grinding wheel ir- 13 respective of whether the carriage 21 moves back (arrow 101) or forth (arrow 102).

Referring again to FIGS. 13 and 14, there is shown another compensating system which is built right into the headstock 76 and which serves to adjust the position of the grinding wheel 75 with respect to the work gear 25 in such a way that the wheel 75 follows movements of the work gear when the latter moves in response to excessive stretching of the tapes.

The intermediate shaft 91 is connected with one element of a friction clutch 160 whose force may be adjusted by suitable resilient means, such as a package of dished springs 161 which !bear against a fixed abutment member 162 and against a second clutch element which is rigid with a lever 163 and which may be rocked by the piston rod 164 of a piston 165. The latter is reciprocable in a double-acting cylinder 166 whose internal chamber is divided into two sections 167, 168 respectively communicating with conduits 169, 170. The means for selectively admitting pressure fluid to the conduits 169, 170 may comprise a suitable valve 166a of known design whose valve member is movable by the cam 114 in response to reciprocation of the carriage 21 on which the pitch disk 28 is mounted.

When the piston 165 reciprocates in response to alternating admission of pressure fluid into the chambers 167, 168, the clutch 160 rotates the intermediate shaft 91 in clockwise and anticlockwise directions whereby the gears 89, 90 rotate the spindle 88 and the nut 87 moves the spindle sleeve 86 with the spindle 78 to shift the grind ing wheel 75 axially and to thereby maintain the active surface 107 of this wheel in constant engagement with a tooth flank 100. In other words, the intermediate shaft 91 may cause such axial movements of the wheel 75, that the surface 107 moves with the tooth flank 100 through a distance 110' or 119, depending on the stretching of the tapes.

The machine of my invention may be resorted to with considerable advantage in mass-manufacturing plants wherein even small savings in time necessary for grinding of one gear add up when very large numbers of gears are being treated in a continuous operation. Heretofore, attempts to shorten the time necessary for grinding the teeth of gear wheels were mainly in a direction to reduce the length of time necessary for removal of a completed work gear and/ or for introduction of the next work gear. Thus, many modern gear grinding machines are equipped with special chutes, magazines and other devices which automatically feed or remove work gears. However, by cutting in half the time necessary for grinding of each tooth flank, the machine of my invention brings about savings which are incomparably greater than savings which may be achieved by streamlining the feed and withdrawal of gears.

It will be noted that FIGS. 1-7 and 13-l4 show fluidoperated compensating means, that FIGS. 810 show electromagnetically operated compensating means, and that FIGS. 11-12 show mechanical compensating means.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be Letters Patent is:

1. A machine for generation grinding of teeth on work gears, comprising a rotary grinding wheel having an annular active surface; deformable rolling motion producing means arranged to reciprocate the work gear in a predetermined path and to simultaneously rock the gear teeth about the axis of the gear so as to impart to a given secured by tooth flank of the gear baok-and-tforth rolling movements with respect to and along the active surface of the grinding wheel whereby the gear is subjected to the action of disengaging forces which result from deformation of said rolling motion producing means and tend to bring about stray movements of the flank in a direction to separate the flank from the active surface during one of such rolling movements; and compensating means arranged to oppose such disengaging forces by automatically compensating for deformation of said rolling motion producing means and to retain said active surface in uninterrupted engagement with the flank.

2. A machine for generation grinding of teeth on work gears, comprising a rotary grinding wheel having an annular active surface; deformable rolling motion producing means arranged to reciprocate the work gear in a predetermined path and to simultaneously rock the gear teeth about the axis of the gear so as to impart to a given tooth flank of the gear back-and-forth rolling movements with respect to and along the active surface of the grinding wheel whereby the gear is subjected to the action of disengaging forces which result from deformation of said rolling motion producing means and tend to bring about stray movements of the flank in a direction to separate the flank from the active surface during one of such rolling movements; and compensating means arranged to automatically compensate for deformation of said rolling motion producing means and to thus retain said active surface in continuous engagement with the flank.

3. A machine for generation grinding the flanks of teeth on work gears, comprising a frame; a rotary grinding wheel mounted on said frame and having an annular active surface; rolling motion producing means comprising supporting means arranged to reciprocate with respect to said frame, a rockable pitch disk mounted on said supporting means, gear-supporting spindle means operatively connected with and arranged to share the movements of said disk, and a pair of flexible tapes each having a first end portion secured to said disk and a second end portion operatively connected with said frame so as to rock said disk in response to reciprocation of said supporting means and to thereby impart to a selected flank of the work gear back-and-forth rolling movements with respect to and along said active surface whereby at least one of said tapes is subjected to the action of stretching forces which tend to separate the flank from said active surface during one of such rolling movements of the flank; and compensating means arranged to automatically shift the second end portion of said one tape so as to compensate for the stretching thereof whereby the flank remains in uninterrupted engagement with said active surface.

4. A machine for generation grinding the flanks of teeth on work gears, comprising a frame; a rotary grinding wheel mounted on said frame and having an annular active surface; rolling motion producing means comprising supporting means arranged to reciprocate with respect to said frame, a rockable pitch disk mounted on said supporting means, gear-supporting spindle means operatively connected with and arranged to share the movements of said disk, and a pair of flexible tapes each having a first end portion secured to said disk and a second end portion operatively connected with said frame so as to rock said disk in response to reciprocation of said supporting means and to thereby impart to a selected flank of the work gear back-and-forth rolling movements with respect to and along said active surface whereby at least one of said tapes is subjected to the action of stretching forces which tend to separate the flank from said active surface during one of such rolling movements of the flank; and compensating means including a braking device arranged to automatically limit rocking movements of said disk so as to automatically compensate for the stretching of said one tape and 15 to retain the flank in uninterrupted engagement with said active surface.

5. A machine for generation grinding the flanks of teeth on work gears, comprising a frame; a rotary grinding wheel mounted on said frame and having an annular active surface; rolling motion producing means comprising supporting means arranged to reciprocate with respect to said frame, a rockable pitch disk mounted on said supporting means, gear-supporting spindle means operatively connected with and arranged to share the movements of said disk, and a pair of flexible tapes each having a first end portion secured to said disk and a second end portion operatively connected with said frame so as to rock said disk in response to reciprocation of said supporting means and to thereby impart to a selected flank of the work gear back-and-forth rolling movements with respect to and along said active surface whereby at least one of said tapes is subjected to the action of stretching forces which tend to separate the flank from said active surface during one of such rolling movements of the flank; and compensating means including deflecting means arranged to automatically reduce the effective length of said one tape so as to automatically compensate for stretching thereof and to retain the flank in uninterrupted engagement with the active surface.

6. A machine for generation grinding the flanks of teeth on work gears, comprising a frame; a rotary grinding wheel mounted on said frame and having an annular active surface; rolling motion producing means comprising supporting means arranged to reciprocate with respect to said frame, a rockable pitch disk mounted on said supporting means, gear-supporting spindle means operatively connected with and arranged to share the movements of said disk, and a pair of flexible tapes each having a first end portion secured to said disk and a second end portion operatively connected with said frame so as to rock said disk in response to reciprocation of said supporting means and to thereby impart to a selected flank of the Work gear back-and-forth rolling movements with respect to and along said active surface whereby at least one of said tapes is subjected to the action of stretching forces which tend to separate the flank from the active surface during one of such rolling movements of the flank; and compensating means including deflecting means arranged to reduce the effective length of said one tape so as to compensate for stretching thereof and to retain the flank in uninterrupted engagement with the active surface, said deflecting means comprising a shaft, a deflecting element mounted on said shaft and adjacent to said one tape, and means for rocking said shaft and for thereby deflecting an intermediate portion of said one tape by said element when said one tape is stretched.

, 7. A machine forgeneration grinding the flanks of teeth on work gears, comprising a frame; a rotary grinding wheel mounted on said frame and having an annular active surface; rolling motion producing means comprising supporting means arranged to reciprocate with respect to said frame, a rockable pitch disk mounted on said supporting means, gear-supporting spindle means operatively connected with and arranged to share the movements of said disk, and a pair of flexible tapes each having a first end portion secured to said disk and. a second end portion operatively connected with said frame so as to rock said disk in response to reciprocation of said supporting means and to thereby impart to a selected flank of the work gear back-and-forth rolling movements with respect to and along said active surface whereby at least one of said tapes is subjected to the action of stretching forces which tend to separate the flank from said active surface during one of such rolling movements .of the flank; and compensating means including deflecting means arranged to reduce the effective length of said one tape so as to compensate for stretching thereof and to retain the flank in uninterrupted engagement with the active surface, said deflecting means comprising a shaft, a deflecting element mounted on said shaft and adjacent to said one tape, and means for rocking said shaft in response to reciprocation of said disk so as to deflect an intermediate portion of said one tape by said element when said one tape is stretched.

8. A machine as set forth in claim 7, wherein said deflecting element is an eccentric which is in constant engagement with and prevents vibrations of said one tape.

9. A machine as set forth in claim 7; wherein the means for rocking said shaft in response to reciprocation of sai i;{disk comprises a friction clutch.

10. A machine for generation grinding of teeth on work gears, comprising a rotary grinding wheel having an active surface; deformable rolling motion producing means arranged to reciprocate the work gear in a predetermined path and to simultaneously rock the gear teeth about the axis of the gear so as to impart to a selected tooth flank of the gear back-and-forth rolling movements with respect to and along the active surface of the grinding wheel whereby the gear is subjected to the action of disengaging forces which result from deformation of said rolling motion producing means and tend to bring about stray movements of the flank in a direction to separate the flank from the active surface during one of said rolling movements; and adjustable compensating means arranged to automatically compensate for deformation of said rolling motion producing means and to thus automatically retain said active surface in continuous engagement with the flank.

11. A machine as set forth in claim 10, wherein said compensating means comprises means for limiting rocking movements of the work gear to movement between two end positions in each of and between which the flank remains in uninterrupted operative engagement with said active surface.

12. A machine for generation grinding the flanks of teeth on work gears, comprising a rotary grinding lwheel having an annular active surface; rolling motion producing means comprising a spindle coaxially connected with the work gear, reciprocating means arranged to reciprocate the spindle in a linear path, and deformable rocking means arranged to rock the spindle about the axis thereof in response to reciprocation of the spindle to thereby impart to a selected tooth flank of the work gear back-and-forth rolling movements with respect to and along said active surface whereby the spindle is subjected to the action of disengaging forces which result from deformation of said rocking means and tend to bring about stray movements of the flank in a direction to separate the flank from the active surface during one .of such rolling movements; and compensating means arranged to automatically hold the spindle against such rocking movements which result from deformation of said rocking means and tend to produce stray movements of the flank and to thereby retain the flank in uninterrupted engagement with said active surface.

13. A machine as set forth in claim 12, wherein said compensating means comprises one-way clutch means having a first clutch element rigid with said spindle, a

second clutch element operative to selectively hold said first clutch element against rocking in said direction such as would cause the flank to become separated from the active surface, and means operatively connected with said reciprocating means to operate said clutch means in response to reciprocation of said spindle.

14. A machine as set forth in claim 13, wherein said one-way clutch means is a friction clutch.

15. A machine for generation grinding the flanks of teeth on work gears, comprising a rotary grinding wheel having an annular active surface; rolling motion producing means comprising a spindle coaxially connected with the work gear, reciprocating means arranged to reciprocate the spindle in a linear path, and deformable rockmg means arranged to rock the spindle about the axis thereof in response to reciprocation of the spindle and to thereby impart to a selected tooth flank of the work gear backand-forth rolling movements with respect to and along said active surface whereby the spindle is subjected to the action of forces which result from deformation of said rocking means and tend to bring about stray movements of the flank with respect to the grinding wheel during each of said rolling movements so that the flank tends to become separated from said active surface during at least one of said rolling movements; and compensating means arranged to automatically hold the spindle against such rocking movements which produce stray movements of the flank on deformation of said rocking means and to thereby retain the flank in uninterr-upted engagement with said active surface, said compensating means comprising a pair of one-way clutch means each arranged to limit one of said rolling movements and each including a first clutch element rigid with said spindle, a second clutch element operative to selectively hold the respective first clutch element against rocking such as would cause the flank to perform stray movements with respect to said active surface, and means operatively connected with said reciprocating means to operate said clutch means in response to reciprocation of said spindle.

16. A machine for generation grinding the flanks of teeth on work gears, comprising a rotary grinding wheel having an annular active surface; rolling motion producing means comprising a spindle coaxially connected with the work gear, reciprocating means arranged to reciprocate the spindle in a linear path, and deformable rocking means arranged to rock the spindle about the axis thereof in response to reciprocation of the spindle and to thereby impart to a selected tooth flank of the work gear back-and-forth rolling movements with respect to and along said active surface whereby the spindle is subjected to the action of forces which result from deformation of said rocking means and tend to bring about stray movements of the flank with respect to the grinding wheel during each of saidrolling movements so that the flank tends to become separated from said active surface during at least one of said rolling movements; and compensating means arranged to automatically hold the spindle such rocking movements which result from deformation of said rocking means and tend to produce stray movements of the flank and to thereby retain the flank in uninterrupted engagement with said active surface.

References Cited by the Examiner UNITED STATES PATENTS 1,405,852 2/1922 Maag et al. 1,832,507 11/1931 Schurr 51-123 2,307,651 1/ 1943 Waldman 51-287 2,347,998 5/ 1944 Drummond 51-287 2,404,573 7/ 1946 Graf 51123 2,850,851 9/1958 Graf 51123 FOREIGN PATENTS 163,665 8/ 1922 Great Britain. 187,663 10/ 1922 Great Britain.

LESTER M. SWINGLE, Primary Examiner. 

1. A MACHINE FOR GENERATION GRINDING OF TEETH ON WORK GEARS, COMPRISING A ROTARY GRINDING WHEEL HAVING AN ANNULAR ACTIVE SURFACE; DEFORMABLE ROLLING MOTION PRODUCING MEANS ARRANGED TO RECIPROCATE THE WORK GEAR IN A PREDETERMINED PATH AND TO SIMULTANEOUSLY ROCK THE GEAR TEETH ABOUT THE AXIS OF THE GEAR SO AS TO IMPART TO A GIVEN TOOTH FLANK OF THE GEAR BACK-AND-FORTH ROLLING MOVEMENTS WITH RESPECT TO AND ALONG THE ACTIVE SURFACE OF THE GRINDING WHEEL WHEREBY THE GEAR IS SUBJECTED TO THE ACTION OF DISENGAGING FORCES WHICH RESULT FROM DEFORMATION OF SAID ROLLING MOTION PRODUCING MEANS AND TEND TO BRING ABOUT STRAY MOVEMENTS OF THE FLANK IN A DIRECTION TO SEPARATE THE FLANK FROM THE ACTIVE SURFACE DURING ONE OF SUCH ROLLING MOVEMENTS; AND COMPENSATING MEANS ARRANGED TO OPPOSE SUCH DISENGAGING FORCES BY AUTOMATICALLY COMPENSATING FOR DEFORMATION ON SAID ROLLING MOTION PRODUCING MEANS AND TO RETAIN SAID ACTIVE SURFACE IN UNINTERRUPTED ENGAGEMENT WITH THE FLANK. 